Vigin vs once fired

Just looking for some advice on what differences if any I can expect from my virgin brass vs same load in once fired.

Now that I have my couple of loads sorted should I go and get
started on my drop chart using new brass or wait until its fire formed to my chamber.

Just to throw in another variable, loaded up some new brass today and only sized the neck because some were a bit skewiff around the mouth and I did read somewhere not to FL size new brass. Anyway, after loading 5 rounds 3 had very stiff bolt closing so I didnt fire and 2 were okay which I fired.

So from here I think I'll just run them all through the FL until the bolt shows a touch of resistance. So back to original question, can I expect any difference between this virgin FL sized brass and the once fired brass when I reload next time around ? Hope this makes sense and I'm not over thinking it

I just did load development for a mates 6.5 284 using Lapua brass. Took over as he was not getting good results with someone else. Other guy had just loaded them straight from the box. Necks were very tight. Ran expander through necks and did load development. 54gns in virgin brass and 53gns once fired for same speed

"Vigin vs once fired"

I would go with the once fired any time!
Why you may ask!!!???
You wont be bringing any meat home with Vigin brass!!!
Just saying :thumbs::thumbs::thumbs:

Just like in real life. You should notice better performance from once fired. And looks like you've already found the tight fitting issue with virgins [emoji1690]

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get yourself a comparator, or just straight out measure everything, and compare.
normally I'd say once fired, but iv had adi and lapua measure the same and shoot the same, never sized them what so ever, new brass from the packet, load and shoot.

We've all seen somebody doing disgracefully well with shelf ammo. That's virgin too. It is to normal spec which quite a few handloaders FL resize back to on 2nd firing anyway. No difference really. But yeah ok if you're doing the light neck size and shoulder bump you will could see less pressure on your second firing.